The study of 2,022 patients identified 63 who had genetic variations considered to be “potentially pathogenic” – capable of producing arrhythmias. Yet their electrocardiograms (ECGs) were no different from those who did not carry the “disease genes.”

The results “warn us to be very careful about returning genetic results, particularly to people who have no signs or symptoms of heart disease,” said the paper’s first author, Sara Van Driest, M.D., Ph.D., assistant professor of Pediatrics and Medicine.

Relying solely on genetic testing without considering the ECG or other data from patients’ electronic medical records (EMRs) not only may alarm them unnecessarily, but also can lead to inappropriate and expensive treatments, in this case, implantation of defibrillators that use electrical shocks to restore normal heart rhythm.

“There’s this big push to return every (genetic) result back to patients,” said senior author Dan Roden, M.D., the William Stokes Professor of Experimental Therapeutics and professor of Medicine and Pharmacology. “This is one way of saying, ‘Hold on. Let’s make sure we’re doing this the right way.’”

Everyone has rare variations in the genetic code that potentially could cause disease, Van Driest added. Many of these variants, however, are actually harmless, as they are found in healthy people. “They’re red herrings thrown into the genome,” she said.

The study’s “silver lining” is that it demonstrates how following a large number of patients through their EMRs over a relatively long period of time can help determine what risk each genetic variation actually carries, she said.

Researchers from several academic medical centers, health care systems and companies contributed to the study, which was conducted and funded in part through the federally funded Electronic Medical Records and Genomics (eMERGE) network.

Vanderbilt has served as the network’s coordinating center since its inception in 2007.